The invention relates to devices for injecting soil treatment liquids into the ground and, more particularly, to such devices including a plurality of reciprocative injection tines having a ground-penetrating tip portion and means for selectively supplying the treatment liquid to the tines only when the tip portions are beneath the ground surface.
The Collins U.S. Pat. Nos. 3,926,131, issued Dec. 16, 1975, and 4,034,686, issued July 12, 1977, disclose injection devices of this type including a crankshaft reciprocating the injection tine and a flow distribution valve connected in timed relation to the crankshaft, via the crankshaft drive chain, for selectively and sequentially supplying the treatment liquid to the tines only when the tip portions are located beneath the ground surface. With this arrangement, setting the timing often can require a laborious trial and error procedure. Also, any slippage of the drive chain during operation can cause the valve to operate out of time in which case the treatment liquid is injected near or on the ground surface rather than at the desired depth beneath the ground surface.
Some prior art constructions for the injection tines include some sort of valve for preventing the flow of treatment liquid from the tines when they are in the raised or non-injection position above the ground surface. However, such valves usually are situated in the flow passage at a location wherein some quantity of the treatment liquid remains in the tines and this residual liquid tends to be shaken out onto the ground during rapid cycling of the tines. Also, the tines used in prior art devices typically employ pointed metal tips which tend to be abraded away after a few operations in some types of soil.
In addition to the above-identified Collins patents, attention is directed to the references referred to therein for examples of prior art constructions for the general type of soil treatment liquid injection devices to which the present invention relates.